I don't think it needs to be any bigger than 1.1x. It could be though, but I'd say it's be 1.2x tops. I generally go with a 1.1x though given Piccolo's lack of 100% certaintity when assuring Majin Vegeta was above kid Gohan.
While Vegeta's comment implies he that level was above Gohan, I like to see Piccolo's comment putting a cap on it. Some ppl see it as Piccolo's memory fading a little while Vegeta had that power more in check as an obsessive warrior thinking about that benchmark. However, the gap isn't so noticeable that, although Vegeta can have a more accurate grasp, Piccolo still remembers things well, especially in regards to the biggest power he had ever felt up until that point and even if coming from someone who wasn't actively thinking of that power like Vegeta, it likely implies the gap isn't big... Noticeable one, but not big or even that considerable. More like in the distant rivaling range.
SSJ2 Pre Majin Vegeta : 81
SSJ2 kid Gohan : 90
SSJ2 Goku : 100
Seems fair enough to me. Some ppl like to push it a little more, while having pre Majin Vegeta closer to SSJ2 kid Gohan, like:
SSJ2 Pre Majin Vegeta : 87
SSJ2 kid Gohan : 90
SSJ2 Goku : 110
Though I generally prefer the first set of gaps.